The present invention relates to a compact, low cost air/fuel mixing valve of the type used in, among other places, commercial and residential cooking ranges that are gas-fueled.
In gas-fueled commercial and residential open top burners, natural gas is introduced at low pressure and mixed with air from a blower. Turndown for each burner is individually controlled after ignition, as from a constantly burning pilot which serves all burners. A source of flame instability and thus inefficient burning has been pressure disturbances caused by gas/air mixer valves being opened and closed to activate or adjust burners.
With known gas/air mixing valves, when a burner corresponding to a valve is desired to be activated, that valve must be opened to allow combustion air to be mixed with gas fuel. Since when not in operation known mixing valves do not draw on the supply of combustion air at all, when the valve is opened it creates a disturbance within the entire combustion air system. This is because the newly opened valve must now either use combustion air that was previously flowing to other burners in the system, thereby decreasing the supply of combustion air available to those other burners, or the combustion air supply means must be triggered to increase its supply. Even when the burner system is of sufficient sophistication to signal for a greater supply of air, the increase will necessarily result in pressure fluctuations which wreak havoc with the burner's efficiency and stability.
In order to compensate for pressure disturbances caused when mixing valves are either first opened or adjusted, known gas-fueled burner systems are often built with combustion air manifolds that are large. This is done to minimize the impact of a pressure drop across one or more mixing valves connected to the manifold. This practice of employing large manifolds to deliver combustion air to burner mixing valves is not, however, without problems.
An important requirement of both commercial and residential cooking ranges is that they be as compact as possible. While the commercial user is driven by the notion that space is money, the residential cooking range user does not welcome any unnecessary invasion of his crucial living space. Accordingly, the awkward and bulky manifold designs offered to compensate for pressure disturbances experienced with known mixing valves have not been satisfactory. Also, even though these large manifolds are able to diminish the impact of mixing valve-induced pressure disturbances, those pressure disturbances have not been eliminated. This continues to create problems, particularly for power burner-type cooking ranges utilizing pressurized combustion air, which are more sensitive to these disturbances than are standard gas-fueled ranges.
It is therefore an object of the present invention to provide a mixing valve for use with gas-fueled cooking ranges that would otherwise be subject to pressure disturbances during ignition or adjustment of a corresponding burner flame.
It is also an object of the present invention to provide such a mixing valve that is compact and easy to manufacture.
It is yet another object of the present invention to provide such a mixing valve that will not require substantial design changes in the other components of the gas-fueled cooking ranges in which it is to be used.
It is still another object of the present invention to enable commercial and residential cooking ranges to burn more efficiently and stably.